# Author: Robert J. Hijmans
# Date : September 2009
# Version 0.9
# Licence GPL v3

	
if (!isGeneric("addLayer")) {
	setGeneric("addLayer", function(x, ...)
		standardGeneric("addLayer"))
}	

setMethod('addLayer', signature(x='Raster'), 
function(x, ...) {

	rasters <- .makeRasterList(...)

	if (! inherits(x, 'RasterStack')) {
		x <- stack(x)
	}

	if (length(rasters)==0) { 
		return(x) 
	}

	if (nlayers(x) > 0) {
		compareRaster(c(x, rasters))
	} else if (length(rasters) > 1) {
		compareRaster(rasters)
	}
		
	vals <- sapply(rasters, hasValues) 
	if (sum(vals) == 0 &  nlayers(x) == 0) { 
		vals[1] <- TRUE 
	}
	if (sum(vals) != length(vals)) { 
		warning('Cannot add a RasterLayer with no associated data in memory or on disk to a RasterStack')
	}
	rasters <- rasters[vals]
	
	if (nlayers(x) == 0) {
		r <- rasters[[1]]
		x@nrows <- r@nrows
		x@ncols <- r@ncols
		x@extent <- r@extent
		x@crs <- r@crs
		if (rotated(r)) {
			x@rotated = r@rotated
			x@rotation = r@rotation
		}

		nl <- 1
		x@layers[[nl]] <- r 
		rasters <- rasters[-1]
		if (length(rasters)==0) { return(x) }
	}

	x@layers <- c(x@layers, rasters)
	names(x) <- sapply(x@layers, names)

	return(x)
}	
)



